Grounding protective device for boats

ABSTRACT

Grounding protective device for sailing vessels and similar boats provided with a fin keel to eliminate to the greatest possible extent the impact effect on a boat when the keel touches ground and to give a long braking distance in order to prevent damage to the boat and the risk of injuries to crew members. A stay is provided in the central plane of the boat which extends from at least either of the end edges of the fin keel at their lower ends to a point so located, that between the point and the fin keel the stay extends at least as deep as any part of the boat.

CROSS REFERENCE TO RELATED APPLICATION(S)

This United States application stems from PCT International ApplicationNo. PCT/SE83/00235 filed June 8, 1983.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to a grounding protective device for sailing andsimilar boats provided with a fin keel.

2. Description of the Prior Art

Sailing vessels or sailing boats are in principle provided with a fixedkeel, which may be designed in two different ways. One keel designcomprises a continuous garboard plate, which extends from prow to sternand mostly is comprised in the hull proper. The second design relates toso-called fin keels, which consist of a garboard plate, which isattached in the central plane of the boat approximately below the centerthereof, and secured in the hull generally by keel bolts. The firstmentioned boat type is called long-keeled boats, and the boat ruddergenerally is attached to the trailing edge of the keel. When such a boattouches ground, the boat runs aground with its middle line against theground, and the grounding mostly proceeds cautiously, so that there isonly small or no damage at all to the boat. The sliding movement of thekeel on the ground produces a relatively soft braking of the speed ofthe boat, whereby a heavy impact on the boat is avoided. The risk ofinjuries for the crew, therefore, is low.

BRIEF SUMMARY OF THE INVENTION

The present invention has the object to eliminate to the greatestpossible extent the effect of the impact on a boat with a fin keel whenthe boat touches ground with the keel. It is essential that boat andcrew are given a long braking distance in order to prevent damage to theboat and injuries to the crew. It is possible, within certain limits, tobuild boats, which are capable of withstanding running aground, buthuman beings cannot be reinforced and, therefore, the braking mustproceed mildly and through a long distance. A further object of theinvention is to eliminate damage to freely suspended rudders of fin-keelboats. In order to achieve the above objects, the invention ischaracterized in that in the central plane of the boat a stay isprovided which extends from at least one of the end edges of the finkeel at the lower end to a point so located that between the point andthe fin keel the stay extends at least as deep as any part of the boat.Fin-keel boats can be understood also to be boats similar to long-keelboats, which at some portion of the keel length, have an inclinationwhich does not allow the boat to slide up on the ground.

BRIEF DESCRIPTION OF THE DRAWINGS

Two embodiments of the invention will now be described in the followingdetailed description, with reference to the accompanying drawingswherein:

FIG. 1 is a schematic elevational side view of a first embodiment of theinvention; and

FIG. 2 is a view similar to FIG. 1 of another embodiment of theinvention.

DETAILED DESCRIPTION

As appears from the figures, a sailing boat with fin keel is shown. Thefin keel is presupposed to be rigidly secured in the lower surface ofthe hull. There exists also fin-keel boats, at which the keel can beretracted into the hull. Although the invention also can be applied tosuch a type of fin keel, it is hereinafter assumed that the fin keel isrigidly secured in the lower part of the hull along the middle linethereof.

Groundings occur most often in such a way, that the ground is locatedbelow the water surface. Accordingly, it is the leading edge of the finkeel which strikes the ground, and the remaining part of the hull passesover the ground. As the ground hereby causes the boat directly andimmediately to stop at the place of contact, a strong impact forcearises which is transferred to the area of attachment between the finkeel and hull. The fin keel generally is so rigid that it is notdeformed, or is deformed very little. This implies that in the contactbetween ground and keel no substantial deformation work arises whichcould reduce the stress caused by the impact force in the area ofattachment between the fin keel and hull. The amount of the impact forcedepends on the weight and speed of the boat. When the speed is notbraked, and deformation work does not arise anywhere during thecollision, then the stress to be taken up in the attachment between thefin keel and hull depends directly on the weight and speed of the boat.In order to limit the braking force on the boat to an amount suitable inview of boat and crew, the braking distance must be relatively long,i.e. of about the same length as the keel. Deformation, for example ofthe leading edge of the keel, therefore, is not a practically possiblesolution. Already at moderate speeds, the damages can be disastrous forthe boat. It is more important, however, that the strong and generallyunexpected impact upon grounding creates a dangerous situation for thecrew whose members often are injured. These injuries are serious per se,but in addition difficulties arise due to the fact that simultaneouslythe maneuvering situation of the boat must be managed. Even if nocatastrophic leakage has been caused, the attachment between keel andhull has been damaged to such a great extent, that the boat is unfit andmust be taken up on land for repair. The damages which could possiblyoccur imply that the hull is smashed in the area where the keel issecured, due to the high torsional moment caused by the impact. Thus, inthe area at the trailing edge of the keel compression occurs, and atension force occurs in the area at the leading edge of the keel in thehull area. These forces are reversed by the present invention and remainreversed until the keel strikes the ground. The hull in the keel areacan be deformed and, in addition, the keel bolts can break or bedeformed permanently and must be replaced. It has happened that sailingboats with fin keels after having grounded at moderate speed have beenregarded as substantially irreparably, i.e. incapable of continuing tosail. In other cases and at milder groundings, considerable damages yetcan be caused, although the hull is not destroyed so that leakageoccurs. The keel bolts can be deformed so that the fin assumes anoblique attitude relative to the central plane of the boat, whichproduces deteriorated sailing of the boat. It is to be mentioned, thatfin-keel boats as they are at present manufactured almost all have thedisadvantage that grounding often causes serious damages. An extremeracing sailing boat always must be taken up as soon as the slightestground contact with the fin keel has occurred. The greatest objective inthe construction of fin-keel boats today should be to attach the finkeel to the hull so that even with slight ground contact no catastropheoccurs and, of course, in cases of sudden brakings no serious risks areinvolved for the crew.

A further problem with fin-keel boats is that the rudder is suspendedfreely from the keel and, thus, a certain distance aft of the trailingedge of the fin keel. It happens quite often that at mild groundings theboat bounces with the keel over the ground in such a way, that theground will be located between the trailing edge of the fin keel and therudder, whereby the rudder will be exposed to the next impact. A rudderin no way can withstand such an impact, and therefore the rudder axlewill break or will be irreparably damaged. The aforesaid applies toentirely freely suspended rudders as well as to rudders provided with asupporting yoke. The present invention, in a second embodiment, preventsto a great extent damage to the rudder when the boat with a fin keelbounces over ground.

The invention becomes apparent from the drawing which shows a stay 1positioned in the central plane of the boat extending from the leadingedge 3 of the fin keel 2 at the lowermost point thereof to the leadingedge 4 of the stem. When this stay 1, for exammple, is a steel wire, itwill, due to its elasticity, be deflected aside if it contacts groundlocated below the draught of the hull but above the lower edge of thefin keel. During a certain period of the grounding the stay can assume aposition shown in FIG. 1 by a dashed line. The impact forces thereby hastwo components, viz. a horizontal one H and a vertical one V. Thevertical component tends to lift the boat over the ground while thehorizontal component H brakes the speed of the boat against the ground.It is understood that the ideal case would be the one where the verticalforce, i.e. the lifting force on the boat also does the entire brakingof the boat. In such a case the impact force is zero at the moment thekeel meets the ground. When the fin, in spite of the fact that brakingwork is carried out, meets the ground, the stay acts as a reinforcingstay and reduces the stresses on the fin attachment.

The stay, as mentioned, can be a steel wire, but other materials canalso be utilized. The essential feature is that braking work is providedby the stay, and the ground is prevented from meeting directly theleading edge of the fin keel. It also is important that the stay isformed so that the smallest possible water resistance is brought aboutby the stay. The stay, therefore, is to be placed in the central planeof the boat and must be streamlined in cross-section in parallel withthe water line of the boat. Due to the inclination of the stay of about25° to the horizontal plane, its section in the flow direction isextended and, thus, more favorable than a vertical stay. In a secondembodiment, also shown in FIG. 1, a stay 5 is inserted between thetrailing edge 6 of the fin keel and a point located at the lower edge ofthe rudder at the pivot center 7 thereof. When the boat bounces overground, the ground is prevented from coming between the trailing edge ofthe fin keel and the leading edge of the rudder 8, and the boatcontinues to side so that the ground cannot strike the leading edge ofthe rudder. The stay 5 also protects a propeller located between the finkeel and rudder from being damaged when the boat bounces over a stone atgrounding.

The stays 1 and 5 should be dimensioned so that when being extendedplastically they never produce forces so high that the mountings of thestays are overloaded and thereby cause hull damage. In FIG. 2 avariation is shown schematically, which consists of a stay 1 that isdesigned superstrong, but the mounting in the leading edge of the hullis made by means of a force-limiting member 9, for example a built-inshear rod, which is attached between the stay 1 and the leading edge 4of the stem, and which breaks before the stresses on the leading edge ofthe stem and/or the leading edge 3 of the fin are so high that damagesmay arise. It is also understood that the member 9 can be formed so thatit extends to absorb tensile load, which implies that the stay can bedesigned rigid and the braking force is absorbed by means of the member9 instead of, or as a complement to, the stay 1 in the event of acollision thereagainst. The member 9 may for this purpose be a spring ora deformable, exchangeable, or replaceable, body.

It is understood that the stays 1 and 5, within the scope of what hasbeen described above, can be designed in different ways and also can begiven different tension. It is advantageous to be able to attach thestay 1 as far as possible ahead, so that the inclination relative to thewater line is minimal. The invention, however, is not restricted in thisrespect, but, depending on the form of the stem line and the form andlocation of the fin keel, two points are selected for attaching the staywhich provide the best possible capacity for absorbing the forces of acollision. It also may be suitable to design the stay mountingsdetachable, so that in racing sailing boats, for example, the stays areattached only during transport to and from the place of racing, butduring the race the stays are removed. It cannot be avoided that thestays yield a certain water resistance, but it should be possible toreduce the resistance to such an extent that the usefulness of the staysin the event of grounding outweighs any disadvantages due to waterresistance.

I claim:
 1. A device for protecting sailing and similar vessels having afixed fin keel when running aground or hitting objects, comprising:anelongated stay attached at one end to the leading edge of the keel atthe lowermost end thereof and extending therefrom in a longitudinaldirection and attached at the other end to the stem edge of the hull ofthe vessel; said stay being positioned with respect to the vessel sothat any point on said stay between said ends is at least as deep as anypart of the vessel between said ends of the stay lying in the samesubstantially vertical plane as said point; and said stay beingelastically or plastically extendable a predetermined extent to absorbshock forces due to impact of objects thereon sufficiently to preventdamage to the keel, hull and attachments at said ends of said stay.
 2. Adevice as claimed in claim 1 and further comprising:a load-limitingmember operatively disposed between at least one of said ends of saidstay and the respective position on the vessel and operable to break ata predetermined load imposed thereon by said stay to prevent damage tothe attachments at the ends of said stay.
 3. A device as claimed inclaim 2 wherein:said load-limiting member comprises means for absorbingtensile stress.
 4. A device as claimed in claim 1, wherein said staycomprises a steel wire having sufficient tensile strength and elasticityto absorb said shock forces.
 5. A device as claimed in claim 3, whereinsaid means comprises a spring.
 6. A device as claimed in claim 3,wherein said means comprises a deformable exchangeable body.
 7. A deviceas claimed in claim 1, wherein the cross-section of the stay parallel tothe water line is streamline-shaped.
 8. A device as claimed in claim 1,wherein said stay is secured detachably at said ends to the vessel.